Finish on a gib

[iron man]

I have been self taught on scraping to straighten out a few minor worn V ways, dovetails and such. I would love to take a scraping class some time when time would permit me to do so. When I was 16 I worked in a machine shop there was a lot of old machines with a lot of old machinist. I was helping tear down and rebuild one of the Milling machines there when we pulled out the knee gib I noticed that someone had done what looked like an engine turned effect on the face of the gib it was nice to look at but we threw it in a box and kept working. It was not done by hand it was machine done it also was not factory because we had a new factory gib ready to go back in. After the re-build the knee was rather catchy and jerky the old machinist I was working with took the old gib out of the parts box and told me this is a better gib put it in and the problem was gone he never explained why I always thought it was because it limited the surface contact area??

 

[Richard King]

The engine marks?? Im not sure what you mean by that...maybe draw it and then take a picture of it and attach it. On some of the old machines they would do a round design that could have put on with a wood dowel with lapping compound, similar to what you might see of a gun. I have been 1/2 moon flaking aprox. 45 years I guess. That's what you see on the top of a Bridgeport table and ways. Some of the factories used a cross checkering like you see on Moore jig bores and G&L boring machines. They called it their signature. Today I use a electric biax 1/2 moon flaker in my job and do it by hand in the classes. Marshall down near Des Moines was trying to organize a class in Iowa, but no one seemed interested. So we canceled it. He is the fellow who bougth the nice planner and posted it's pictures here. Many people assume when they send you a new gib it is ready to install, but they are machined close, but they should be scraped to fit the taper, get at lest 12 points per 1 inch. I now say 20 points because you can get 20 by accident with a biax electric scraper. The wiggle with the new gib was beacuse the taper was off or the gib was probably high in the middle. Most of the time the ways are worn low in the middle and you have to leave the gib loose or it will get stuck or tight on the extreme ends. I hope that makes sense. Rich

 

[iron man]

Thanks for the reply what it looked like was like what you described with a wood dowel and lapping compound but a bit more agressive like a small wire brush spun at high speed. We use to call this an engine turned effect they use to do it on flat panels on the dashes of cars and on airplane spinners it has a very neat looking effect most of the time it is done in aluminum. The dovetail was re-machined so it was straight but the new gib was sticky through out the range the one with the nice design in it was not did this limit surface contact?? Ray

 

[Richard King]

Thanks for the reply what it looked like was like what you described with a wood dowel and lapping compound but a bit more agressive like a small wire brush spun at high speed. We use to call this an engine turned effect they use to do it on flat panels on the dashes of cars and on airplane spinners it has a very neat looking effect most of the time it is done in aluminum. The dovetail was re-machined so it was straight but the new gib was sticky through out the range the one with the nice design in it was not did this limit surface contact?? Ray

Ideally we try to get 50% high and 50% low spots . The high points carry the weight and the low spots hold the oil. Sort of looks poka dot oil and high spot. The stick effect is called stick slip and it like rubbing 2 gage blocks to- gether and they wring together and there is no low oil pockets so it jerks. Another this when lets say as screw or move the a saddle toward the operator and it gets tight and when you screw it toward the back it gets easier to move, I would assume the gig screw is broken or it may have one gib screw in the front and one in the back and the back one is missing or loose alowing the gib to move and bind up as it tightens on the taper. This may not be thecse in your gib Iron man, but its for the benefit for the others reading the post. Rich

 

[iron man]

Thanks the stick/slip answered my question that I have wondered about all these years it is exactly what I thought was going on.. Thanks Ray

 

[Richard King]

To all of you who have the jerking motion on your gib, you can see what he said on this post. One thing that we now have that can help someone who runs out of adjustment on gibs, is a Teflon based product called Rulon, Turcite, a Graphite/nylon product called Nylatron that can be epoxied to the worn side of the gib that are self lubricating and really work well with lube, so you do not need to buy a new gib. Times have changed. Rich